Study On the Tribological Behavior of the Arc-added Glow Discharge Plasma Non-hydrogen Carburization On Titanium Alloy Surfaces

This paper introduces a new titanium alloys surface strengthening treatment by using the arc-added glow discharge plasmas non-hydrogen Carburization technique. High purity and high strength graphite is selected as cooling cathode arc source for supplying carbon atoms and particle, which migrate to the titanium alloy(Ti6A14V) surface and form modified layer. Thus, the hydrogen embrittlement is avoided while the tribological behavior of the titanium alloy surface is improved in the respects of anti-friction and anti-wear ability.The tribological behavior of the modified layer under dry sliding against SAE52100 steel was evaluated on a ball-on-disc test rig. The results showed that the modified layer obtained a thickness of 30u,m at 980°C, 30minutes. The microhardness of the Ti6A14V alloy surface attained 936 HV, which was much larger than that of the T16A14V alloy. The TJ6A14V alloy was characterized by adhesion wear and scuffing under dry sliding against the steel, while the surface modified layer experienced much abated adhesion wear and scuffing under the same testing condition. This could be attributed to the carbon element with different modalities exists in the modified layer. The modified layer showed good friction-reducing and fair anti-wear ability in dry sliding against the steel. Using the SEM, XRD and XPS, the phase structure and morphology of the Carburization modified layer was analyzed.

Plasma surface alloying with molybdenum and carburization of TiAl based alloys

A hard layer which is rich in Mo and carbon on the surface of TiAl based alloy was formed after plasma Mo alloying followed by plasma carburization. The process parameters of plasma Mo alloying and plasma carburization were modified. The chemical composition and the thickness of the formed layer are obviously affected by the temperature used during alloying and carburization. The surface layer of TiAl treated by carburization at 1000℃ following Mo alloying at 1125℃ consists of a hard layer with thickness of 20μm and has a graded distribution in chemical composition. The pin-on-disk wear test shows that the frictional properties of TiAl disk treated only by carburization are improved. The TiAl surface treated by both Mo alloying and carburization possesses lower friction coefficient than that of carburized TiAl.

On the Plasma (ion) Carburized Layer of High Nitrogen Austenitic Stainless Steel

The manganese concentration of austenitic stainless steel decreases from the inner layer towards the surface of the plasma (ion) carburized layer due to the evaporation of manganese from the specimen surface. The carbon concentration in the carburized layer is influenced by alloyed elements such as Cr, Ni, Si, and Mo, as well as Nitrogen. This study examined the effects of nitrogen on the properties of the carburized layer of high nitrogen stainless steel. Plasma (ion) carburizing was carried out for 14.4 ks at 1303 K in an atmosphere of CH4+H2 gas mixtures under a pressure of 350 Pa. The plasma carburized layer of the high nitrogen stainless steel was thinner than that of an austentric stainless steel containing no nitrogen. This suggested that the nitrogen raised the activity of carbon in the plasma carburized layer, GDOES measurement indicated that the nitrogen level in the layer did not vary after plasma (ion) carburizing.

INTERGRANULAR EMBRITTLEMENT IN PLASMA CARBURIZED LAYER

This paper deals with the cause of intergranular fracture occurred in the retained austenitic region in plasma carburized layer.The results show that the presence of retained austenite, which has a good effect on the impact toughness,has no relation to this embrittlement.Analy- sis by Auger electron spectroscopy shows that the impurities S and P segregate at the grain boundaries is the main reason of the intergranular embrittlement in carburized layer. However,the segregation of P and S can be removed by reheating and quenching treatment.

Study on Carburizing and Temperature Rising of the Semi-Steel Melt with Plasma Heating

Experiments were carried out on carburizing and temperature rising of the semi steel melt in a plasma induction furnace.Influence of many factors, such as power supply mode,position of the plasma torch and bottom blown gas stirring,on heating efficiency and melt temperature distribution was studied. Melt temperature could be effectively controlled by plasma heating,and carbon content of semi steel melt increased from 1.92 % to 4.58 %, and the utilization rate of carbon reached up to 61.57 % during carburizing of the melt.

Effect of carbon on tribological property of plasma carburized TiAl based alloy

Plasma carburization at two different methane-to-argon gas ratios (5:5 and 6:5) was carried out on the cast TiAl based alloy of Ti-46.5Al-2.5V-1Cr (mole fraction, %) in order to enhance its wear resistance. The results show that after carburization under both carburizing atmospheres, Ti2AlC and TiC are the main carbides in the carburized layer and the value of surface hardness reaches more than HK 822, but for the carburized TiAl treated at CH4:Ar of 5:5, the surface carbon concentration is higher and the carburized depth is slightly thicker than that of alloy carburized at CH4:Ar of 6:5. The result of the ball-on-disk test against hardening-steel counter bodies shows that the wear resistance of the TiAl based alloy carburized under two different carburizing atmospheres is improved compared with non-carburized TiAl. The tribological property is related to the carbon content, and the carburized layer obtained at CH4:Ar of 5:5 possesses a stable friction coefficient, lower volume loss or wear rate and narrow wear scar. The characteristic of the carburized layer was examined by using optical microscopy, glow discharge spectrum and micro-hardness tester.

Effect of process parameters on induction plasma reactive deposition of tungsten carbide from tungsten metal powder

Tungsten carbide deposit was made directly from tungsten metal powder through the reaction with methane in radio frequency induction plasma. Effect of major process parameters on the induction plasma reactive deposition of tungsten carbide was studied by optical microscopy, scanning electron microscopy, X ray diffraction analysis, water displacement method, and microhardness test. The results show that methane flow rate, powder feed rate, particle size, reaction chamber pressure and deposition distance have significant influences on the phase composition, density, and microhardness of the deposit. Extra carbon is necessary to ensure the complete conversion of tungsten metal into the carbide.

Evaluation of Microstructure and Wear Properties of Ti-6Al-4V Alloy Plasma Carbonized at Different Temperatures

Ti-6A1-4V （TC4） alloys were plasma carbonized at different temperatures （900, 950, and 1 000 ℃） for duration of 3 h. Graphite rod was employed as carbon supplier to avoid the hydrogen brittleness which is ubiquitous in traditional gas carbonizing process. Two distinguished structures including a thin compound layer （carbides layer） and a thick layer with the mixed microstructure of TiC and the a-Ti in carburing layer were formed during carburizing. Furthermore, it was found that the microstructure and the properties of TC4 alloy were significantly related to the carbonizing temperature. The specimen plasma carbonized at 950 ~2 obtained maximum value both in the hardness and wear resistance.

Synthesis of titanium carbide by induction plasma reactive spray

A novel method capable of sufficient mixing of titanium powder and methane of carbon source was developed in the synthesis of titanium carbide by induction plasma reactive spray. X ray diffraction analysis, optical microscopy, scanning electron microscopy, and microhardness test were used to characterize the spray formed deposit. The experimental results show that both primary carburization of the titanium particles inside the plasma flame and secondary carburization of the growing deposit on high temperature substrate contribute to the forming of titanium carbide. The transitional phase of TiC 1- x has the same crystal structure as TiC, but has a slightly low lattice constant. The deposit consists of fine grain structure and large grain structure. The fine grain structure, harder than large grain structure, shows grain boundary fracture.

Trend of Nitriding on Chromium-Molybdenum Steel via Low Temperature Screen Plasma Technology

Low temperature screen plasma technology, a high plasma density, through using a low energy supply, shows excellent effects on a low alloy chromium-molybdenum steel for plastic molds because it does not show a compound layer and a high surface hardness without a deterioration in matrix hardness. For interest about hardening depth, both the screen plasma nitriding and plasma nitro-carburizing processes were tested including nitrogen, hydrogen and a methane mixed gas environmental at 653 K, 713 K. The optical emission spectroscopy (OES) has been analyzed during screen plasma nitriding (SPN) and a nitro-carburizing process (SPNC) was proceeded at 713 K and the same pressure. I find it difficult to dissociate nitrogen molecules perfectly with neutral nitrogen atoms via the DC-plasma nitriding process. Therefore, the SPN and SPNC process have shown a high density of plasma species even though low temperature plasma conditions have a high peak intensity of Hβ and Hγ in the results of the analysis by OES. The hardness value was measured with the micro-Vickers hardness tester after the SPN, SPNC process and the chemical composition of nitriding layers were traced by GDOES. The screen nitriding layer via the screen plasma technology has shown excellent properties with a thickness depth of about 850 ~ 900 HV without the deterioration of matrix hardness value.

ICP-AES法测定炼钢用增碳剂中二氧化钛含量

通过碳酸钠、四硼酸钠等碱性混合助熔剂熔解增碳剂试样,用盐酸、热水熔解熔球,过滤得到稳定的待测溶液。使用电感耦合等离子体发射光谱法,测定待测元素的光谱强度,从而得到其含量。实验表明:本法较灰分成分分析,无须检测灰分,分析快速,方法的精密度和正确度满足要求。

甘油体系中不锈钢表面液相等离子体电解渗碳工艺

采用液相等离子体电解渗方法,在80%甘油水溶液中实现了304不锈钢表面快速渗碳。研究施加电压和放电时间对渗碳过程的影响,分析了渗碳层的显微组织,并比较了不同工艺条件下渗碳层显微硬度分布。结果表明:经过5 min的快速放电处理,渗碳层厚度接近100μm,硬度达到880 HV。在350 V和3 min渗透条件下渗碳层质量较好。

甘油浓度对不锈钢表面液相等离子体电解渗透过程的影响

以50%～90%(体积分数)甘油水溶液为电解液,研究304不锈钢表面液相等离子体电解快速渗碳工艺;分析不同甘油浓度和电压下渗碳层的显微组织、相组成和显微硬度。结果表明,随甘油浓度的提高,渗透电压上升,渗碳层厚度增加,渗碳层硬度增大,最大硬度达到762HV;且渗碳层中固溶碳的奥氏体(γC)含量急剧增加,但碳化物含量降低。在80%(体积分数)甘油水溶液和电压350 V工艺条件下获得的渗碳层质量较好。

离子渗碳温度对316L不锈钢渗层组织和性能的影响

利用低温离子渗碳技术,在不同温度下对AISI 316L奥氏体不锈钢进行渗碳处理。利用光学显微镜、显微硬度计、XRD以及电化学测试技术研究了渗碳温度对不锈钢表面显微组织和性能的影响。结果表明,渗碳温度显著影响AISI 316L奥氏体不锈钢渗碳层的组织结构与性能。渗碳温度在400-550℃之间时,可以获得无碳化物析出的、具有单一γc相结构的渗碳层;渗碳温度在550℃时,渗碳层为γc相＋Cr23C6＋Cr7C3＋Fe3C＋Fe2C的混合组织。渗碳层的厚度与硬度均随渗碳温度的升高而增加。550℃是AISI 316L奥氏体不锈钢中铬的碳化物析出的临界温度。为了避免铬的碳化物析出而降低不锈钢的耐蚀性能,奥氏体不锈钢渗碳必须在低于550℃的渗碳温度下进行。

不锈钢在甘油体系中等离子体电解渗碳层特性研究

以甘油+20%水溶液为电解液,利用液相等离子体电解渗技术在AISI304不锈钢表面成功实现了快速渗碳。分析了渗碳层的组织结构,并评估了渗碳层与GCr15钢球对磨时摩擦学行为。结果表明,经过3min/350 V等离子体电解渗处理,渗碳层深度达到85μm,最大显微硬度达到762 HV0.02。干摩擦条件下,渗碳层的磨损率比不锈钢基体降低了一个数量级。

奥氏体不锈钢低温离子渗碳

为避免奥氏体不锈钢在渗碳过程中析出铬的碳化物而降低其原有的耐蚀性能,开发了低温离子渗碳处理技术。利用低温离子渗碳技术对AISI 316L、AISI 321和AISI304三种不同类型的奥氏体不锈钢进行了渗碳处理,并对不锈钢渗碳层组织和性能进行了研究。结果表明,渗碳温度、渗碳时间和基体材料成分对渗碳层的组织和性能都有重要的影响。渗碳温度在400～550℃时,AISI 316L和AISI 321不锈钢可以获得无碳化物析出的具有单一γc相结构的渗碳层;XRD分析结果证实了550℃是AISI 321和AISI 316L奥氏体不锈钢的临界渗碳温度,500℃是AISI 304不锈钢的临界渗碳温度,在此温度以上渗碳时,渗碳层有铬的碳化合物析出;含有Mo或Ti的奥氏体不锈钢（AISI 316L,AI-SI 321）和不含Mo或Ti的不锈钢（AISI 304）相比,在400～500℃渗碳时可以获得较好的渗碳层。

渗碳温度对Ti_2AlNb合金摩擦磨损性能的影响

利用双辉等离子表面冶金技术,在不同温度下对Ti_2AlNb合金进行渗碳处理。研究不同渗碳温度对Ti_2AlNb合金微观组织、显微硬度及摩擦磨损性能的影响。结果表明:整个渗碳层包括石墨沉积层、硬质碳化物层和扩散层,其厚度随渗碳温度的增加而增加。从硬质碳化物层到基体,试样硬度呈梯度递减规律;且工艺温度越高,渗碳硬度曲线越平缓。在970、1050和1100℃制备的渗碳试样的比磨损率分别是基体的1/14.67,1/14.96和1/16.64,其平均摩擦因数均小于基体,表现出良好的减摩和耐磨性能,磨损机制为磨粒磨损。

表面高铬高碳合金层的研究

采用双层辉光等离子表面合金化方法 ,在A3钢表面形成高铬高碳表面合金化层。合金层中的碳化物细小、弥散、均匀 ,且不含粗大共晶莱氏体组织 ,硬度高 ,耐磨性好。与GCr15淬火钢相比 ,耐磨性提高 8.

奥氏体不锈钢离子渗碳后的腐蚀行为

为了提高奥氏体不锈钢零件的使用寿命,利用低温离子渗碳技术对AISI316L奥氏体不锈钢进行了表面渗碳处理。用X射线衍射仪和光学显微镜分析了渗碳层的微观组织结构,用显微硬度计测试了渗碳层的硬度分布,通过电化学极化曲线测试技术和化学腐蚀试验研究了离子渗碳AISI316L不锈钢的腐蚀行为。渗碳层为单相碳过饱和奥氏体固溶体,由此明显提高了AISI316L不锈钢的抗腐蚀性能,渗碳层硬度梯度平缓,表面显微硬度高达900HV。结果表明,奥氏体不锈钢低温离子渗碳处理不仅提高了其表面硬度,而且提高了不锈钢表面的耐腐蚀性能,从而提高了其使用寿命。

TiAl合金离子渗碳摩擦磨损性能研究

对TiAl合金进行离子渗碳处理以提高其耐磨性.利用摩擦磨损试验机对TiAl渗碳后的室温及600℃高温干摩擦磨损性能进行了研究,采用扫描电镜、能谱、辉光放电光谱仪、X射线衍射仪等手段观察分析了磨痕的形貌和成分以及渗碳层组织与相结构.研究表明,TiAl合金经离子渗碳处理后形成一定厚度的含硬质Ti2AlC的渗碳层,其室温摩擦系数和磨损量明显低于TiAl基材,表现出良好的减摩和耐磨性能,600℃高温摩擦系数与TiAl基材相当,但磨损量较低,耐磨性得到提高.